1. Field of the Invention
This invention relates to the field of dual stage actuated (DSA) suspensions for disk drives. More particularly, this invention relates to the field of electrical connections to microactuators on DSA suspensions.
2. Description of Related Art
Magnetic hard disk drives and other types of spinning media drives such as optical disk drives are well known. Disk drive suspensions are the assemblies that hold the read/write head over the correct place on the spinning data disk, in order to write data to, and read data from, the desired data track on the disk.
Both single stage actuated disk drive suspensions and dual stage actuated (DSA) suspension are known. In a single stage actuated suspension, only a voice coil motor moves the disk drive suspension. In a DSA suspension, as for example in U.S. Pat. No. 7,459,835 issued to Mei et al. as well as many others, in addition to the voice coil motor which moves the entire suspension, at least one secondary actuator, often referred to as a microactuator, is located on the suspension in order to effect fine movements of the magnetic head slider to keep it properly aligned over the data track on the spinning disk. The secondary DSA microactuator(s) provide much finer control and much higher bandwidth of the servo control loop than does the voice coil motor alone which effects relatively coarse movements of the suspension and hence the magnetic head slider. Lead zirconium titanate is one of the broadly used intermetallic inorganic compounds possessing piezoelectric properties and is commonly referred to as PZT. PZT devices are often used as the microactuator motor, although other types of microactuator motors are possible. Examples of a dual stage actuated suspension, a PZT microactuator often referred to simply as a PZT for short, and various methods of electrically and mechanically integrating the PZT into the suspension, are disclosed in U.S. Pat. No. 8,570,688 to Hahn, and in copending U.S. patent application Ser. No. 14/045,773, which are owned by the assignee of the present application. Other mechanical and electrical connections have been proposed.
Various structures and methods have been proposed for making the required electrical connections to the PZT microactuators. One structure and method that was developed by the assignee of the present application is shown in FIG. 1, and in FIG. 2 which is a cross sectional view taken of the suspension of FIG. 1 taken along section line 2-2. In this example, suspension 10 includes slider 12 mounted to gimbal 14. The PZT 20 is connected to gimbal 14 through gimbal arms 16. The PZT 20 typically includes PZT material 22, a thin top metalized electrode 24, and thin bottom metalized electrode 26. A flexible circuit 30 typically includes a metal support layer such as stainless steel layer 32, insulating layer such as polyimide layer 34, and a copper signal conductor layer including copper electrical contact pad 37 covered by an anti-corrosion layer 38 such as nickel followed by gold. Anti-corrosion layer 38 will be referred to hereafter simply as gold layer 38. Non-conductive adhesive such as non-conductive epoxy 50 physically attaches PZT 20 to the flexible circuit 30 on one side. For the electrical connection, bottom electrode 26 of PZT 20 is physically and electrically connected to the ground potential of the suspension body by conductive epoxy 18 bonded to grounded suspension body 16 which is stainless steel. The driving voltage potential is provided through conductive epoxy or solder balls 52 that forms a physical and electrical bridge from a copper contact pad 37 and its anti-corrosion layer 38 on the flexible circuit 30 to the metalized top surface of the PZT which defines the top electrode 24.